When a sewage plant in Nogales, Arizona made significant upgrades in 2009, the ripple effects were enormous for a once algae-coated Upper Santa Cruz River.
“It was overnight. Immediately. Fish were suddenly in the water,” Birdie Stabel said as she waded through a knee-deep stretch of the river near Tubac, Arizona. Until then, the level of nitrogen had been too high.
For two decades, Stabel has not only watched this river come back to life; she has measured it for a variety of things such as chlorine, dissolved oxygen, electro conductivity and temperature.
It’s a monthly ritual that a handful of volunteers called Friends of the Santa Cruz River are carrying out on this grey morning. Years ago, Stabel said they didn’t know this information would be of any use.
"But when it came time to get the funding for the sewage treatment plant to be expanded, our data was very important because they could measure exactly how things had changed,” she said.
The plant treats millions of gallons of wastewater from Mexico and southern Arizona each day and then empties it into the river. Now with the improved water quality, native plants and wildlife have re-emerged.
“It's full of trees. It’s just gorgeous. You hear grey hawks calling, " Stabel said just as a red-tailed hawk cried in the background.
'Everybody is concerned about losing the effluent'
In fact, last year marked the first time in a decade the endangered Gila topminnow repopulated these waters - a testament to how this habitat has rebounded thanks to the discharge of treated water into what would otherwise be a dry river. It’s a precious resource that Stabel and other devotees of the Santa Cruz realize can’t be taken for granted.
“Everybody is concerned about losing the effluent. We have been so fortunate to have it these years," she said.
That’s not an issue here yet, but travel north to the Lower Santa Cruz and some of that water could be in jeopardy. Two treatment plants near Tucson sustain habitat and wildlife in the stretch of the river, as well.
The Bureau of Reclamation has proposed diverting about 7,000 acre feet of that treated water from the river to a nearby irrigation district.
“What we have been trying to do is maximize the value of the effluent,” Bureau of Reclamation spokesman Lawrence Marquez said.
In much of central and southern Arizona, the state gives credits when effluent is put into the ground – think of it like a bank account. If the effluent goes into a river instead, the state only gives half a credit.
“If state law allowed you to get the same value for the effluent, we would certainly consider leaving it in the river. There would be no reason to take it out,” he said.
Marquez said this temporary pilot project will give the Bureau of Reclamation more revenue, by selling those credits, and will allow it to meet its obligations under a decades-old Native American water rights settlement.
He said an environmental analysis shows the diversion won’t have major impacts, but conservationists like Ian Dowdy, a program director with the Sonoran Institute, which has studied the river extensively, disagree. They contend it will hurt an already water-stretched river.
“We need to find a mechanism where water that’s being applied to the environment that is making its way into our aquifers can receive a fair amount of credit,” Dowdy said.
'Increasing conflict'
Central Arizona has been a leader in re-using its wastewater. More than 80 percent is recycled – from irrigating golf courses to replenishing the water table.
The state doesn’t track all the rivers that depend on effluent, but the University of Arizona, several years ago, identified at least nine different waterways.
“We anticipate there will be increasing conflict over the use of this particular resource in the future," said Dave White, a professor at Arizona State University who studies sustainability.
In the coming decades, Arizona will need to meet a projected supply gap of 1 to 3 million acre feet of water. While effluent is only a small fraction of the state’s overall water budget, he said it’s a critical and affordable source.
“Arizona does not currently have an adequate policy framework for both encouraging and for managing the environmental uses for wastewater,” White said.
In many cases, effluent makes it into a river incidentally - not as part of a broader state plan.
Friends of the Santa Cruz River's Birdie Stabel acknowledges the river isn’t constant. It’s always been subject to the human and environmental pressures of the Southwest.
“I’m a little hopeful that if we are proactive, something can be done to keep enough water in the river," she said, adding it’s not going to by survive by default.
